Clean-in-place (CIP) techniques use the combination of chemistry and mechanical action to clean the inside of a system without requiring the time consuming and labor intensive disassembly and manual cleaning of a system. CIP cleaning regimens are adapted for removing soils from the internal components of tanks, lines, pumps and other process equipment. Methods and systems for CIP cleaning are frequently used, for example, to clean processing equipment with liquid product streams, such as those used in the food and beverage, pharmaceutical, textile and laundry industries. Further discussion of CIP operations can be found for example in U.S. Pat. Nos. 6,197,739, 6,953,507 and 6,991,685, the complete disclosures of which are herein incorporated by reference in their entirety.
CIP operations generally include the circulation of chemistries (e.g., detergents, antimicrobials and the like) for periodic cleaning of a system. Often CIP methods involve a first rinse, the application of cleaning solutions, a second rinse with portable water, followed by resumed operations. The process can also include any other contacting step in which a rinse, acidic or basic functional fluid, solvent or other cleaning component such as hot water, cold water, etc. can be contacted with the equipment at any step during the process. In addition, a final portable water rinse step may be skipped in order to prevent contamination of the equipment with bacteria following the cleaning and/or sanitizing steps. Prior to resuming normal processing, chemistry residues are removed from the system and/or any product contacted by the cleaning chemistry is discarded.
There is an increasing demand for development of suitable compositions for CIP applications, including chemistries useful for cleaning, sanitizing and disinfecting. Onsite production of cleaning chemistries is also under increasing demand. Onsite chemistry production can be achieved through electrolysis of water and electrolytes to produce alkaline detergent solutions of sodium hydroxide (NaOH), hypochlorite solutions or chlorine for use as detergent, bleach, surface sanitizers and other disinfectant purposes. The electrolysis of water and salt using this process is well established. A basic solution of sodium hydroxide (or “caustic” or “alkali”) as well as an acidic solution of hypochlorous acid is formed. Depending upon the structure of an electrochemical cell, various effluents may be produced. For example, a cell divided by a membrane(s) produces both hypochlorous acid and sodium hydroxide. Alternatively, an electrochemical cell not divided by a membrane produces sodium hypochlorite (commonly referred to as bleach). Products obtained from electrolysis of water and salt solutions provide a source of chlorine-based detergent and disinfectant having numerous cleaning and sanitizing capabilities. These chlorine-containing oxidants are biocidal agents that are effective in killing bacteria, viruses, parasites, protozoa, molds, spores and other pathogens.
Use of electrolysis solutions for CIP applications generates high and variable concentrations of chlorine requiring chlorine measurement to maintain concentrations sufficient for cleaning and sanitizing without reaching levels that are corrosive to CIP systems. As a result, accurate chlorine measurements are necessary for electrolytic CIP solutions. However, commercially-available chlorine monitors are designed for detecting less concentrated chlorine levels, such as those associated with water treatment methods (from about 0.5 ppm to about 3 ppm). See e.g., U.S. Pat. No. 5,422,014, describing the pH limitations of chlorine monitors, the complete disclosure of which is herein incorporated by reference in its entirety. As a result, chlorine content achieved from electrolysis solutions, pH variability in water supply to an electrolytic solution and/or water used to dilute electrolysis solutions preclude chlorine measurement as required for use of electrolytic solution for CIP applications.
Accordingly, it is an objective of the claimed invention to develop control systems and methods for measurable automated chlorine output for automated recirculating or single-pass cleaning systems, such as CIP applications.
A further object of the invention is to develop systems and methods for use of electrolysis solutions based on having measured correct chlorine oxyanion concentration.
A further object of the invention includes systems and methods for hands-free automation of chlorine measurement over broad ranges of pH.